The subject of this invention is fuel and propellant composition of fuel containers/cells, used for gas combustion powered tools, including powered fastener driving tools, and more specifically changes to the formulations of such fuels for enhancing tool performance.
Combustion powered fastening tools are widely used in construction and other industries and many consumer applications. Suitable examples of such tools are described in U.S. Pat. Nos. 4,403,722; 4,483,474; 4,522,162; and 8,302,831, all of which are incorporated by reference. Combustion tools are usually powered by liquefied hydrocarbon fuel, stored in aerosol dispensers, sometimes called fuel cells, containers or cartridges, delivering fuel in aerosol form to a tool combustion chamber to be mixed with air and ignited to combust and provide energy for inserting a fastener into a work piece. Inside the fuel cell container, the fuel is stored in a flexible bag or pouch with an outlet valve configured for connection with a fuel delivery system for metering doses of fuel to the combustion chamber. Exemplary fuel cells are described in U.S. Pat. Nos. 5,115,944 and 7,661,568 which are incorporated by reference.
Usually, the fuel contained in a collapsible bag of such fuel cells includes a single component or a mixture of two or more components, typically liquefied hydrocarbon gases, plus a small amount of a lubricant. A propellant, contained within the cell but outside the collapsible fuel bag, is usually also a single component or a mixture of two or more liquefied hydrocarbons, in combination with air, nitrogen, or other gases. The propellant has a higher vapor pressure than the fuel pressure and maintains the fuel in a liquefied state during operation.
One commonly used fuel used to power combustion powered fastening tools, on market since 2001, is a two-component fuel sold by ITW Paslode. The ITW fuel includes as its main components, propylene (137 psig at 21° C.) and 1-butene, mixed in different percentages to meet local conditions and regulation requirements of particular markets. The highest vapor pressure mix of this fuel family is known at 90 psig at 21° C. A variation with a three-component fuel also has vapor pressure at 90 psig at 21° C. The propellant in these cases is propylene with or without atmospheric air. Conventional fuel cell fuels do not have vapor pressures exceeding 90 psig at 21° C.
U.S. Pat. No. 8,205,777 describes the work of a fuel cell/container, and claims fuel formulations of 40-95% of 1-butene plus 60-5% of propane and also 56-96% of 1-butene plus 44-4% of propylene. For the purpose of this application, it should be noticed that in the '777 patent, none of the claimed combinations produces fuel with vapor pressure higher than 82 psig at 21° C.
U.S. Pat. No. 6,800,104 discloses a combustion tool fuel composition having a fragrance to mask the often unpleasant odor of conventional fuels. While dealing mostly with fuel fragrances of 3-component fuels, this reference fails to disclose fuel component combinations to exceed 90 psig at 21° C. Notably, propylene is disclosed in the preferred composition in approximately 10 percent by weight.
A common problem of users of combustion tools is that tool performance degrades as temperatures fall. It has been found that the rate of tool misfire increases at lower temperatures, usually below 40° F./5° C. These performance problems make the tool less desirable to users, who need to work efficiently in a variety of weather conditions.
Thus, there is a need for an improved combustion tool fuel that enhances tool performance at low temperatures.